Monitoring toxic gases is a concern in relation to environmental pollution, occupational health, and industrial emission control. Known methods and apparatuses have been developed to detect the presence of gas. For example, gas chromatography, ion chromatography, electrolytic conductivity detection, and conductometric measurement are typically used to detect gas. However, these manners for detecting gas have generally been expensive, cumbersome, shown to have poor sensitivity and slow response times. They also typically cannot readily be used for on-line measurements. Other manners for monitoring include capacitance sensors and surface acoustic wave sensors. However, the sensitivities, or detection capabilities, of these devices generally fall in the range of low-ppm to high-ppb. Electrochemical sensors were provided to overcome these limitations. Electrochemical sensors typically operate at room temperature, provide a signal which varies with concentrations of analyte species, have short response time, and exhibit acceptable sensitivity, stability, and reproducibility. In addition, electrochemical sensors are compact and can be used for continuous monitoring.
Electrochemical gas sensors usually detect the presence of gases with sufficient reliability and accuracy. However, if the humidity of the sample gas to be measured within the sensor is different than the humidity of the atmosphere surrounding the sensor, which is typically used to determine the baseline of the measurement, a sensor's accuracy may be compromised. The greater the difference in humidity, the less likely the sensor will accurately detect a gas.
In addition, raising a temperature of the sensor may negatively affect its accuracy. At elevated temperatures, which may be any temperature above room temperature, sensors are believed to lose ionic conductivity due to dehydration, which generally worsens over time and which may include dehydration of the electrolytic material, electrolyte solution, or both. Without adequate hydration, the accuracy of measurements taken across the sensing electrode may be compromised. Although the sensor may be refilled with electrolyte or solution to correct the problem, the process may need to be repeated numerous times and, due to the repeated interruptions of the experiment and increased human intervention, this may compound the problem.
In some cases, a low temperature of a sensor may also negatively affect accuracy. A lower temperature may cause the electrolyte to freeze the flow of ions through the electrolyte or electrolytic material to be hampered. As a result, the response of the sensor may not be consistent with sensor readings at room temperature.